DNA-based monitoring of the alien invasive North American crayfish Procambarus clarkii in Andean lakes (Ecuador)

In 2013 the red swamp crayfish (Procambarus clarkii) was introduced in Lake Yahuarcocha, a tropical, high altitude lake located in the Andes of northern Ecuador. Abundance of this alien invasive species has increased to such extent that it is disturbing the autochthonous aquatic ecosystem. Little is known about its distribution throughout Ecuador. Monitoring is therefore important to assess the current distribution and to control future spread. A molecular method based on environmental DNA (eDNA) was developed and used to assess the distribution of P. clarkii at 21 sites in Lake Yahuarcocha, and three sites each at Lake Caricocha and Lake San Pablo in the Ecuadorian highlands. The molecular detection of crayfish from water samples was compared to capture based distribution patterns obtained from traditional trapping. Results showed an eDNA detection accuracy of 86% in water samples, without false positives. The results indicate that this budget-friendly method is easy to use and can provide important information on the occurrence of alien invasive species in the tropics.